Design and analysis of decoupled tetra-polar ring-coils for wireless power transfer in rotary mechanism applications

摘要

Decoupling of same-sided coils is a critical issue for multi-input and/or multi-output inductive power transfer (IPT) systems. The mutual inductance between the same-sided coils may lead to the system detuning and the decrease of power transfer capacity and efficiency. In this study, a tetra polar ring coils (TPR-coils) and its decoupling method are proposed for IPT systems applied to rotary mechanism. Firstly, an analytical expression, which illustrates the relationship between the mutual inductance and geometric parameters of coaxial cylindrical helical coils, is given. Then the equivalent circuit model of TPR-coils is established, and the mutual inductance constraints for the decoupling of TPR-coils are proposed. Combined with the expression of mutual inductance, a geometric parameter solution of decoupled TPR-coils is derived. The correctness of theoretical analysis is verified by finite element method simulations and experiments. The experimental results show that the mutual inductance between the same-sided coils can be reduced to 0.6 mu H, and the effectiveness of TPR-coils is also verified on an IPT prototype with 231 W power and over 86% efficiency.